chromium/third_party/abseil-cpp/absl/crc/internal/non_temporal_memcpy.h

// Copyright 2022 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_
#define ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_

#ifdef _MSC_VER
#include <intrin.h>
#endif

#if defined(__SSE__) || defined(__AVX__)
// Pulls in both SSE and AVX intrinsics.
#include <immintrin.h>
#endif

#ifdef __aarch64__
#include "absl/crc/internal/non_temporal_arm_intrinsics.h"
#endif

#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstring>

#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace crc_internal {

// This non-temporal memcpy does regular load and non-temporal store memory
// copy. It is compatible to both 16-byte aligned and unaligned addresses. If
// data at the destination is not immediately accessed, using non-temporal
// memcpy can save 1 DRAM load of the destination cacheline.
constexpr size_t kCacheLineSize = …;

// If the objects overlap, the behavior is undefined. Uses regular memcpy
// instead of non-temporal memcpy if the required CPU intrinsics are unavailable
// at compile time.
inline void *non_temporal_store_memcpy(void *__restrict dst,
                                       const void *__restrict src, size_t len) { … }

// If the objects overlap, the behavior is undefined. Uses regular memcpy
// instead of non-temporal memcpy if the required CPU intrinsics are unavailable
// at compile time.
#if ABSL_HAVE_CPP_ATTRIBUTE(gnu::target) && \
    (defined(__x86_64__) || defined(__i386__))
[[gnu::target("avx")]]
#endif
inline void *non_temporal_store_memcpy_avx(void *__restrict dst,
                                           const void *__restrict src,
                                           size_t len) { … }

}  // namespace crc_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_CRC_INTERNAL_NON_TEMPORAL_MEMCPY_H_